Tin based white metal bearing alloys producing good bond with backing material

ABSTRACT

A TIN BASED WHITE METAL BEARING ALLOY HAVING A HIGH ELONGATION AND CAPABLE OF PRODUCING A GOOD BOND WITH A BACKING MATERIAL, WHICH IS COMPOSED OF 1.0-2.9% BY WEIGHT OF COPPER, 5.0-13-.0% BY WEIGHT OF ANTIMONY, 0.11.5% BY WEIGHT OF CADMIUM, 0.001-0.1% BY WEIGHT OF BERYLLIUM, 0.005-0.2% BY WEIGHT OF CHROMIUM AND THE REMAINDER CONSISTING OF TIN.

Aug. 6, 1974 Filed Nov. 6, 1972 TENSILE STRENGTH (Kg /mm NOBUKAZU MORISAKI 3,827,884 TIN BASED WHITE METAL BEARlNG ALLOYS FRODUCING GOOD BOND WITH BACKING MATERIAL ,3 Sheets-Sheet 1 FIG. la

INVENTIVE ALL APPLICANT'S ALLOY \OF PRIOR INVENTON 3 S\ & L CONVENTIONAL ALLOY FIG. lb

APPLICANT'S ALLOY EgJigQ o PRIOFJNVENTION -T' CONVENHONAL ALLOY l I I 2 29 3 4 Aug. 6, 1974 Filed Nov.

ELONGATION HARDNESS (HV) NOBUKAZU MoRIsAKI 3,827,884 TIN BASED WHITE MEIALI BEARING ALLOYS PRODUCING GOOD BOND WITH BACKING MATERIAL 6, 1972 3 Sheets-Sheet ,3

F|G.|c

INVENTIVE 25 ALLOY v N IE IIIIII'IVEI TIN 2O- I l5 ls Q 1 T CONVENTIONAL ALLOY I l I I I I 2 2.9 3 4 I FIG. Id

APPLIcANT's ALLOY'OF 'NVENT'VE l'PRlOR INVENTION 3O ALLOY a 20 CoNvENTIoNAu ALLOY l l I l I 2 2.9 3 4 Cu (36) Aug. 6, 1974 NOBUKAZU MORISAK! 3,8

TIN BASED WHITE METAL BEARING ALLOYS PRODUCING GOOD BOND WITH BACKING MATERIAL Z5 Sheets-Sheet 5 Filed Nov.

United States Patent Olfice 3,827,884 TIN BASED WHITE METAL BEARING ALLOYS PRODUCING :GOOD BOND WITH BACKING MATERIAL Nobukazu Morisaki, Nagoya, Japan, assignor to Daido Metal Company, Nagoya, Japan Continuation-impart of abandoned application Ser. No.

78,546, Oct. 6, 1970. This application Nov. 6, 1972,

Ser. No. 303,837 The portion of the term of the patent subsequent to Feb. 16, 1988, has been disclaimed Claims priority, application Japan, July 15, 1970, 45/61,420 Int. Cl. C22c 13/00 US. Cl. 75-175 A 1 Claim ABSTRACT OF THE DISCLOSURE A tin based white metal bearing alloy having a high elongation and capable of producing a good bond with a backing material, which is composed of 1.02.9% by weight of copper, 5.0l3.0% by weight of antimony, 0.1- 15% by weight of cadmium, 0.001-0.1% by weight of beryllium, 0.0050.2% by weight of chromium and the remainder consisting of tin.

CROSS-REFERENCE TO RELATED APPLICATION ance and fatigue strength higher than those of conventional tin based white metals, by finely dividing the crystals in the e-phase (Cu Sn and in the fi-phase of the conventional tin based white metal by the addition of cadmium, beryllium and chromium, and filed the same as Japanese Patent Application No. 7,755/68 (Japanese Patent Publication No. 17,065/70).

The present invention has been achieved with a view to further improving the bonding property of the abovedescribed alloys with respect to the backing material, as

well as improving the available percentage of the material in a mass production, and providing bearing alloys which are completely free of failure when used as a hearing.

The previously proposed tin base white metal bearing alloys mentioned above which have a fine crystal structure and high tensile strength, toughness, impact resistance and fatigue strength, are characterized by being composed of 543% by weight of cadmium, antimony, 3-9% by weight of copper, 0.1-1.5 by weight of 0001-01 by weight of beryllium, 0.005-0.2% by weight of chromium and the remainder consisting substantially of tin. The present invention hasbeen achieved based on the dis covery that, by reducing the copper content of the previously proposed alloys to 1-2.9% the elongation (percent) of the alloys and the bonding strength (kg/mm?) of the same with a backing material, which is a veryimportant characteristic of a bearing can be increased. The

reductionin copper content also has such advantageous effect that, in the practice of casting, particularly in the centrifugal casting of the alloys to make a bearing, segregation of the e-phase (Cu Sn can be prevented; the bonding property of the alloys with respect to a backing material can be improved; and the casting operation be- 3,827,884 Patented Aug. 6, 1974 comes easy. It has been confirmed through experiment that, while the reduction in copper content results in a slight lowereing of the tensile strength and hardness of the alloys, such lowering is not so significant as will degrade the performance of the product bearing, but on the other hand, a bearing alloy of fine structure capable of producing a good bond with a backing material can be obtained, and further that the subject alloys are not substantially inferior to the previously proposed alloys of the present inventor in respect of toughness, impact resistance and fatigue strength.

The present invention will be described in further detail by way of example hereunder with reference to the accompanying drawings, in which:

FIGS, 1a, 1b, 1c, 1d are diagrams illustrating the influence of the Cu content on the mechanical properties of the tin based white metal bearing alloys according to the present invention;

FIG. 2 is a picture showing the microscopic structure of a conventional tin based white metal bearing alloy at a magnification of FIG. 3 is a picture showing the microscopic structure of the tin based white metal alloy of the present invention at the same magnification;

FIG. 4 is a microscopic picture showing the boundary of the conventional tin based white metal bearing alloy and a backing material bonded together; and

FIG. 5 is a microscopic picture showing the boundary of the alloy of the present invention and the backing material bonded together.

FIGS. la, 1b, 1c and 1d illustrate the influence of the Cu content on the mechanical properties of the inventive alloy, applicants alloy of prior invention and conventional alloy each consisting essentially of the table below.

TABLE I Chemical composition (in weight percent) Cu Sb Cd Cr Be Sn Inventive alloy Applicant's alloy of prior Conventionalalhy 1-4 8.4 Remainder.

As may be understood from FIG. 1a, the alloys of the present invention are far improved in the bonding strength as compared with those of the applicants prior invention and other conventional alloys. Further, when the Cu content is reduced, the crystallization of the ephase (Cu Sn in the boundary layer with the backing metal is minimized and thereby the bond is improved, and concurrently the grains of e-phase (Cu Sn are refined and uniformly distributed in the alloys of the present invention by the cooperating and cumulative effect of Cd, Cr and Be added, whereby the bonding property is further improved in the alloys of the present invention than the applicants alloys of the prior invention.

It will be also understood from FIGS. lb, 1d that lowering of the tensile strength and the hardness due to the decrease of Cu content is compensated by the addition of Cd, Cr and Be. It will be seen from FIGS. 10, 1b, 1c and 1d, that by reducing the Cu content to 1 2.90%, the elongation can be increased markedly, without substantially degrading the tensile strength and hardness, and further the crystals in the e-phase and the fi-phase can be finely divided and hence the segregation of the crystals can be prevented and the amount of Cu in solid solution can be decreased, which increases the bonding strength of the alloy with the backing material, improves the available percentages and facilitates the casting operation.

Now, the properties of the tin based white metal bearing alloy according to the present invention, a conventional alloy of the type being discussed and the alloy previously proposed by the present inventor, are compared in the table below:

portions consisting of a black matrix are the bearing alloys. FIG. 4 is a microstructure of the conventional tin based bearing alloy, in which it will be seen that a large TABLE II Composition, percent Property Tensile Elonga- Herd- Bonding strength, ion ness, strength, Cu Sb Sn Other kg./mm.' (percent) Hv kgJmm.

Alloy oi the invention 1.06 8.82 Remainder" Cd, Be, Cr.. 8.55 23.4 24.7 10.7 2.05 8. 76 Cd, Be, Cr.. 9.01 21.0 26. 1 i 10.0 2.31 8.66 d, Be, r 9.08 20.3 26.2 9.8 2.52 8.85 Cd, Be, CL. 9.13 19.8 26.5 9.5 2. 68 8.77 Cd, Be, r.. 9. 19 19. 1 26. 9.3 2.83 8.73 Cd, Be, Cr.. 9.22 18.5 26.8 9.3 2.90 8.80 Cd, Be, Cr 9.25 17.9 26.9 9.0

Alloy oi the applicant's prior application 3.00 8. 65 Remainden- Cd, Be, CL. 9. 26 17. 1 27. 0 8. 77 3.81 8.54 do Cd, Be, CL- 11.1 18.8 31.9 7.4 4.09 8.71 do Cd, Be, Cl... 9.59 11.6 28.2 7.28

Conventional alloy 3.71 7.06 Remainder 7.55 14.0 24.0 5.6 5. 43 0. 53 8.30 8.0 27.0 5.3 3.16 7.15 do Cd, Ni, Ag" 9.3 14.4 27.9 6.8

As will be clear from the above table, the alloy according to the present invention is superior not only to the conventional alloy but to the alloy previously proposed by the present inventor, with respect to both elongation and bonding strength. In the table above, the bonding strength was obtained by preparing a sample piece of bearing alloy strip with backing material attached thereto having a width of B (mm.) and having two parallel grooves formed from the outer surface of the bearing alloy and the outer surface of the backing material to a depth reaching the bounding planes thereof, the interval between the grooves being L (mm.), pulling the sample piece by gripping both ends thereof, measuring the tensile load (kg.) when the backing material and bearing alloy strip were separated and dividing the tensile load thus measured by the bonding area B x L (mmfi). The fatigue strength which is as important as the bonding strength for a bearing, was tested using the same fatigue tester as used and under the same conditions as in the prior application of the present inventor. Namely, the fatigue strength was measured by lining a backing material, consisting of steel, with an alloy to be tested by centrifugal casting to produce a sample bearing having an inner diameter of 6.2 mm. and a width of 31 mm. A rotary shaft was journaled in the sample bearing and rotated at 3000 r.p.m. at a peripheral speed of 9.7 m./sec. under a load of 250 kg./cm. continuously with forced lubrication. The time when the area of cracked region of the bearing had reached i5% of the total area of projection of the bearing surface, was regarded as a fatigue limit. As as result of the test, it was found that the bearing comprising the alloy of this invention is not subjected to noticeable cracks even after subjecting to 50 hours of testing, similar to the alloy of the prior invention, and is superior to the conventional alloy and less inferior to the alloy of the prior invention in respect of fatigue resistance. In addition, the alloy of this invention is superor to that of the prior invention in respect of elongation and bonding strength. Therefore, it will be obvious that the alloy of the invention will exhibit excellent performance when used as a bearing which is used under a relatively low load.

Referring to FIGS. 2 and 3, there are shown microstructures (100x) of the conventional alloy and the alloy of the present invention. In these microscopic pictures, it will be clearly noted that the e-phase (Cu Sn and the B-phase (SbSn) of the alloy of this invention are extremely finely divided as compared with those of the conventional alloy. In FIGS. 4 and 5 which show microscopic structure of the bonding area between the backing material and the alloy, the lower white portions area carbon steel for mechanical structures (SlOC) used as a backing material having ferrite grains. The upper amount of white, coarse, acicular e-phase (Cu Sn and square fl-phase (SbSn) are present at the boundary of the bearing alloy and the backing material. In contrast thereto, in the bearing comprising the alloy of this invention, as shown in FIG. 5, the e-phase is finely divided and is small in amount, and the contact area between the soft bearing alloy matrix etched in black color and the similarly soft ferrite matrix of the backing material, at the boundary ofsaid alloy and said backing material, is extremely larger than that in the case of FIG. 4.

From the fact that the amount of the fragile e-phase is small and the contact area between the soft matrixes of the backing material and the bearing alloy is large, it will be assumed that the bonding strength would be obviously high, and such assumption is substantiated by the test result.

As described above, according to the present invention the bonding property of a tin based white metal bearing alloy with respect to a backing material is improved by finely dividing the e-phase and the fl-phase by the addition of small quantities of cadmium, beryllium and chromium, and also by restricting the formation of the e-phase within a necessary minimum range by limiting the amount of copper to be added tothe range from 1 to 2.90%. Therefore, use of the alloy according to the invention in a mass production of bearings, is advantageous in reducing the rate of rejection due to unsatisfactory bond, in the casting operation, particularly in the centrifugal casting operation, and further in substantially decreasing the failure of the product bearings due to separation of the alloy from the backing material in use. Thus, the present invention enables the available percentage and safety of the bearings to be improved and makes a great contribution to the industry.

What is claimed is:

1. A tin based white metal bearing alloy having a high elongation and being capable of producing a good bond with a backing material, which is composed of 1.0-2.90% by weight of copper, 5.0l3.0% by'weight of antimony, 0.1-1.5% by weight of cadmium, 0.001- 0.l% by weight of beryllium, 0.005-O.2% by weight of chromium and the remainder tin.

References Cited UNITED STATES PATENTS 3,563,732 2/1971 Morisaki 75175 A L. DEWAYNE RUTLEDGE, Primary Examiner E. L. WEISE, Assistant Examiner UNITED STATES PATENT OFF ICE CERTIFICATE OF CORRECTION Patent No. 3,827,884 Dated August 6, 1974 Nohuk.azu MQrisak It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1', line 6', should read:

Daido Metal Company, Ltd. Nagoya, Japan Signed and sealed this 19th day of November 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. v C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM po'wso (10-59) I I USCOMM-DC we're-Poo a v a u. s. soviizuusm rnnrrme ornc: um o-au-ssl. 

